Fetches type-design-performance from aaronontheweb/dotnet-skills and configures it for Cursor.
3
Select Cursor when prompted
The CLI shows a list of agents. Use arrow keys and space to select Cursor:
◆ Which agents do you want to install to?
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│ ── Universal (.agents/skills) ────────────────
│ · Cline · Codex · Goose · Windsurf
│ ●Cursor(selected)
│ · Cursor · Aider · Continue
4
Verify installation
Confirm successful installation by checking the skill directory location:
.cursor/skills/type-design-performance
Restart Cursor to activate type-design-performance. Access via /type-design-performance in your agent's command palette.
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Security Notice
We perform automated surface-level scans (Gen AI Scanner, Socket, Snyk) during installation. These checks detect common vulnerabilities but do not guarantee complete security. Always review skill source code and verify the publisher's reputation before production use.
Skills execute code in your environment. Always review source, verify the publisher, and test in isolation before production.
Seal your types - Unless explicitly designed for inheritance
Prefer readonly structs - For small, immutable value types
Prefer static pure functions - Better performance and testability
Defer enumeration - Don't materialize until you need to
Return immutable collections - From API boundaries
Seal Classes by Default
Sealing classes enables JIT devirtualization and communicates API intent.
// DO: Seal classes not designed for inheritancepublicsealedclassOrderProcessor{publicvoidProcess(Order order){}}// DO: Seal records (they're classes)publicsealedrecordOrderCreated(OrderId Id,CustomerId CustomerId);// DON'T: Leave unsealed without reasonpublicclassOrderProcessor// Can be subclassed - intentional?{publicvirtualvoidProcess(Order order){}// Virtual = slower}
Benefits:
JIT can devirtualize method calls
Communicates "this is not an extension point"
Prevents accidental breaking changes
Readonly Structs for Value Types
Structs should be readonly when immutable. This prevents defensive copies.
// DO: Readonly struct for immutable value typespublicreadonlyrecordstructOrderId(Guid Value){publicstaticOrderIdNew()=>new(Guid.NewGuid());publicoverridestringToString()=> Value.ToString();}// DO: Readonly struct for small, short-lived datapublicreadonlystructMoney{publicdecimal Amount {get;}publicstring Currency {get;}publicMoney(decimal amount,string currency){ Amount = amount; Currency = currency;}}// DON'T: Mutable struct (causes defensive copies)publicstructPoint// Not readonly!{publicint X {get;set;}// Mutable!publicint Y {get;set;}}
When to Use Structs
Use Struct When
Use Class When
Small (≤16 bytes typically)
Larger objects
Short-lived
Long-lived
Frequently allocated
Shared references needed
Value semantics required
Identity semantics required
Immutable
Mutable state
Prefer Static Pure Functions
Static methods with no side effects are faster and more testable.
// DO: Static pure functionpublicstaticclassOrderCalculator{publicstaticMoneyCalculateTotal(IReadOnlyList<OrderItem> items){var total = items.Sum(i => i.Price * i.Quantity);returnnewMoney(total,"USD");}}// Usage - predictable, testablevar total = OrderCalculator.CalculateTotal(items);
Benefits:
No vtable lookup (faster)
No hidden state
Easier to test (pure input → output)
Thread-safe by design
Forces explicit dependencies
// DON'T: Instance method hiding dependenciespublicclassOrderCalculator{privatereadonlyITaxService _taxService;// Hidden dependencyprivatereadonlyIDiscountService _discountService;// Hidden dependencypublicMoneyCalculateTotal(IReadOnlyList<OrderItem> items){// What does this actually depend on?}}// BETTER: Explicit dependencies via parameterspublicstaticclassOrderCalculator{publicstaticMoneyCalculateTotal(IReadOnlyList<OrderItem> items,decimal taxRate,decimal discountPercent){// All inputs visible}}
Don't go overboard - Use instance methods when you genuinely need state or polymorphism.
Defer Enumeration
Don't materialize enumerables until necessary. Avoid excessive LINQ chains.
// BAD: Premature materializationpublicIReadOnlyList<Order>GetActiveOrders(){return _orders
.Where(o => o.IsActive).ToList()// Materialized!.OrderBy(o => o.CreatedAt)// Another iteration.ToList();// Materialized again!}// GOOD: Defer until the endpublicIReadOnlyList<Order>GetActiveOrders(){return _orders
.Where(o => o.IsActive).OrderBy(o => o.CreatedAt).ToList();// Single materialization}// GOOD: Return IEnumerable if caller might not need all itemspublicIEnumerable<Order>GetActiveOrders(){return _orders
.Where(o => o.IsActive).OrderBy(o => o.CreatedAt);// Caller decides when to materialize}
Async Enumeration
Be careful with async and IEnumerable:
// BAD: Async in LINQ - hidden allocationsvar results = orders
.Select(async o =>awaitProcessOrderAsync(o))// Task per item!.ToList();await Task.WhenAll(results);// GOOD: Use IAsyncEnumerable for streamingpublicasyncIAsyncEnumerable<OrderResult>ProcessOrdersAsync(IEnumerable<Order> orders,[EnumeratorCancellation]CancellationToken ct =default){
Implementation Guide
Prerequisites
›Claude Desktop or compatible AI client with skill support
›Clear understanding of task or problem to solve
›Willingness to iterate and refine outputs
Time Estimate
15-45 minutes depending on use case complexity
Steps
1Install skill using provided installation command
2Test with simple use case relevant to your work
3Evaluate output quality and relevance
4Iterate on prompts to improve results
5Integrate into regular workflow if valuable
Common Pitfalls
⚠Expecting perfect results without iteration
⚠Not providing enough context in prompts
⚠Using skill for tasks outside its intended scope
⚠Accepting outputs without review and validation
Best Practices
✓ Do
+Start with clear, specific prompts
+Provide relevant context and constraints
+Review and refine all outputs before using
+Iterate to improve output quality
+Document successful prompt patterns
✗ Don't
−Don't use without understanding skill limitations
−Don't skip validation of outputs
−Don't share sensitive information in prompts
−Don't expect skill to replace human judgment
💡 Pro Tips
★Be specific about desired format and style
★Ask for multiple options to choose from
★Request explanations to understand reasoning
★Combine AI efficiency with human expertise
When to Use This
✓ Use when
Use when skill capabilities match your task, clear ROI on time saved, and you can validate outputs. Best for repetitive tasks, learning, and quality improvement.
✗ Avoid when
Avoid when task requires deep expertise you can't validate, involves sensitive decisions, or when learning process is more valuable than speed of completion.
Learning Path
1Familiarize yourself with skill capabilities and limitations
2Start with low-risk, non-critical tasks
3Progress to more complex and valuable use cases
4Build expertise through regular use and experimentation
